Not that I know much about...

Not that I know much about Pyroclastic flows, I seem to remember the Beeb did a program on Pompeii and Herculaneum. If I remember rightly, a huge column of hot air, ash and boulders is sent up and when it collapses, it falls down the side of the volcano at very high speed and temperature. If one was coming, you might outrun it if you were in a supersonic plane but not otherwise, so I am quite pleased to hear that you didn't see one! I'd say that your interpretation that they are not a good thing is accurate. Miss Murph may have found out more in NZ as there is still quite a lot of activity there I believe, though I haven't heard of any reports of pyroclastic clouds there!

Heading South?